Ignition distributor



July 23, 1963 Filed NOV. 16, 1961 R. K. FRANK 3,098,366

IGNITION DISTRIBUTOR 4 Sheets-Sheet l INVENTOR. AOfiE/PT K. F/PA/VK ATTORNEY July 23, 1963 R. K. FRAYNK 3,098,366

IGNITION DISTRIBUTOR Filed Nov. 16, 1961 4 Sheets-Sheet 2 I 70 li 90 5 I 5 INVENTOR. RO6EA7' A. FRA/VK ATTORNEY July 23, 1963 R. K. FRANK 3,098,366

IGNITION DISTRIBUTOR Filed Nov. 16, 1961 4 Sheets-Sheet 3 147'7'O/P/VEY July 23, 1963 R. K. FRANK IGNITION DISTRIBUTOR Filed Nov. 16, 1961' 4 Sheets-Sheet 4 yyaaeza WV.) /1// JIM/may yaw .9

INVENTOR. ROBERT A. FRANK Va TOR/V5) United States Patent ration of Michigan Filed Nov. 16, 1961, Ser. No. 152,829 6 Claims. (CI. 6425) This invention relates to ignition distributors, and more particularly to an improvement in ignition distributors of the type in which spark advance is effected in whole or in part by the action of centrifugal weights driven in accordance with engine speed.

In a number of ignition distributors commercially available today, a pin extending from each of the centrifugal weights slides in a slot formed therefor in an arm extending laterally from the distributor cam. An alternate construction employs suitably oriented slots formed in the centrifugal weights; in this case, the pins sliding in the weights are formed on or secured to each arm of the distributor cam member. In either case, the geometry of this pin and slot linkage is such that it produces the de sired cam rotation to weight displacement (spark advance) characteristic.

A distributor of this kind in which the pins are formed on the distributor cam member is disclosed in US. application Serial No. 84,254 filed on January 23, 1961, in the names of Eugene C. Bettoni and Ernest R. Larges.

While distributors of this kind have been generally successful in their operation, the use of a cylindrical pin in a slot having parallel and straight edges results in straight line contact between the pin and the wall of the slot. This relatively small contact area results in very large bearing stresses due to vibratory conditions due to engine torsionals and the reaction of the cam to the rubbing block forces, even at light loads. These high bearing stresses often cause severe wear of both the pin and the slot.

The above-mentioned wear in turn results in a number of highly undesirable effects in the function of the spark advance mechanism, as follows:

(1) The distributor provides a different amount of spark advance for a given r.p.m. depending upon whether the engine was accelerated or decelerated to reach the given r.p.m.

-(2) The distributor fails to follow the original desired relationship between spark advance and r.p.m.

In US. application Serial No. 143,277 entitled, Ignition Distributor, and filed on October 4, 1961, in the name of Ian I. C. Scott, it was proposed to eliminate the above undesirable effects and to greatly increase the life of a distributor of this kind and insure its continued original proper performance. In the particular embodiment of the invention disclosed therein, this was acocmplished by enlarging the above-mentioned slots and providing a so-called slider block having oppositely disposed fiat outer surfaces and being made of any suitable wear-resistant and self-lubricating material, such as Delrin, between the pin and the slot. In other words, the slider block was formed in a manner so that it could be assembled over the pin and be inserted into the slot, thus increasing the contact surface area between the pin and the slot. Wear was thus drastically reduced and/or virtually eliminated, and the useful life of the distributor and advance mechanism was greatly prolonged.

It was also pointed out in the above referenced application Serial No. 143,277 that even in a new and properly operating prior art distributor such as that shown in application Serial No. 84,254 there is some hysteresis between the increasing speed and the decreasing speed spark advance curves; this is so, even though both curves are within the prescribed limits. However, it was found that this hysteresis was greatly reduced and/or entirely eliminated with the use of the proposed slider block. It was believed that this was due in part to the edges of the slots having machine marks extending in one direction or the other, depending upon the direction of the machining; this roughness was sufiicient to give a different coefficient of friction when the pin was moving along the edge of the slot in one direction than when the pin was moving in the other direction. The surface of the self-lubricating slider block appeared to merely glide over the high spots of this roughened surface on the edges of the slots so as to more nearly result in a constant coefiicient of friction, regardless of the direction of movement.

It was also pointed out that both the pins and the weights in present day prior art distributors have to be hardened, in most cases to somewhere around R 55 as a minimum. This hardening is an expensive step in the manufacture of the distributor. With the use of the softer Delrin or other material for the slider block proposed in application Serial No. 143,277, neither the pins nor the slots have to be hardened; rather, they can be used in their unhardened and machined condition.

While the structure proposed in application Serial No. 143,277 very effectively eliminated the above mentioned problems with prior art distributors, it still requires the forming or securing of pins, either on the centrifugal weights or on the arms extending from the distributor cam member. This has now been found to be an unnecessary expensive step in the production of distributors of this kind. Also, the combination pin and slider block is a two-piece construction which also adds to the expense.

Accordingly, an object of this invention is to eliminate the above recited objections to prior art distributors.

Another object of the invention is to provide a distributor construction in which the attachment of pins and the two-piece pin and slider block construction are eliminated.

A still further object of the invention is to substitute a single-piece combination pin and slider block for the previously proposed two-piece assembly.

Other objects and advantages of the invention will become more apparent when reference is made to the following description and the accompanying drawings, wherein:

FIGURE 1 is a top plan view of a prior art ignition distributor to which the invention may be applied so as to improve the operation thereof;

FIGURE 2 is a cross-sectional view taken substantially on the plane of line 22 of FIGURE 1 and looking in the direction of the arrows;

FIGURE 3 is a cross-sectional view taken on the plane of line 3-3 of FIGURE 2 and looking in the direction of the arrows;

FIGURE 4 is a view similar to FIGURE 3 wherein the distributor centrifugal advance mechanism has been modified to embody the invention;

FIGURE 5 is a cross-sectional view taken on the plane of line 55 of FIGURE 4 and looking in the direction of the arrows;

FIGURE 6 is a view similar to FIGURE 5 illustrating the application of the invention to a dis-tributor in which certain parts are reversed;

FIGURE 7 is anenlarged perspective view of the combination pin and slider block element embodying the invention;

FIGURE 8 is a graph illustrating the ignition advance characteristics of an ignition distributor before and after the above-mentioned wear that use of the invention eliminates.

As already stated above, FIGURES 1-3 illustrate one of the present-day distributors to which the invention may be applied. For purposes of clearly distinguishing the invention from the prior art, this prior art distributor will first be described. Following that, the manner in which the invention may be applied to this and other prior art distributors will be described.

Referring now to the drawings, FIGURES 1-3 illustrate a carburetor having an induction passage 12 and a throttle valve 14 adapted to control the flow of combustible mixtures therethrough and into the engine intake manifold 16. Port 18 communicates with the induction passage 12 and with the chamber 22 of the vacuum motor 24, as by means of a suitable conduit 26.

The ignition distributor 28 is comprised generally of a cup-shaped housing 30 including a depending reduced portion 32 having an opening 34 therethrough for the reception of a driving shaft 36. A bushing-like bearing member 38 may be provided in order to reduce the degree of friction between the rotating shaft 36 and surface of opening 34.

A base plate 40, rigidly secured to the housing 30 as by means of screws 42, retains a pivot member 44 to which the breaker plate 46 is pivotally secured. The breaker plate 46 carries thereon a breaker arm assembly 48 which includes a cam engaging portion 50 engageable by the rotating cam 52 to effect make and break of the circuit at the contacts indicated at 54. The cam 52 is mounted on the shaft 36 for limited rotation with respect thereto, but so as to be rotated thereby. The shaft 36 is, of course, rotated in timed relation with the engine 56 by means of gear member 58 cooperating with some output transmission 60 of the engine.

The pressure responsive device 24 is substantially comprised of a housing 62 and cover member 64 rigidly held together in a manner so as to peripherally secure a diaphragm member 66 therebetween. A member 68, connected at its one end to the diaphragm member 66, is adapted to be operatively engaged with breaker plate 46, as by means of a hole formed therein for the reception of a connecting link 70 which pivotally secures the member 68 and breaker plate 46 to each other. Chamber 22, formed generally by cover 64 and diaphragm 66 is exposed to a source of vacuum, as communicated by conduit 26, while chamber 72 is vented to the atmosphere. A calibrating spring 74 is also located within chamber 22 in a manner so as to resiliently oppose the movement of diaphragm 66 in response to increases in vacuum. The entire pressure responsive devce 24 can, of course, be secured to the housing 30 by any suitable meanssuch as screws 76.

The speed responsive portion of the ignition advance mechanism, as illustrated generally by FIGURE 3, is substantially comprised of flyweight members 78 and 80 which are pivotally mounted, as by pivot members 82 and 84, respectively, to a base member 86. The base member is rigidly secured by any suitable means such as a collar member 88 to the shaft 36 so as to rotate therewith.

A cam plate 90, rigidly secured to the lower portion of cam member 52, has slots 92 and 94 formed therein, which are adapted to cooperate with cylindrical pin-like members 96 and 98 secured within or to flyweight members 78 and 80. Calibrating springs 100 and 102 anchored at one end to the base member 86 are provided to resist the outward movement of the flyweights 78 and 80 as engine speed increases.

The ignition distributor, as illustrated by FIGURES 1, 2 and 3, is shown in full retard, as it would be when the engine is running at curb idle.

As engine speed increases, the rotational speed of shaft 36 will correspondingly increase, and the flyweights 78 and 80 will travel arcuately outwardly about their pivots 82 and 84. As the flyweights move outwardly, the motion transmitting links or pins 96 and 98 rotate cam plate 90 and cam member 52 counterclockwise with respect to shaft 36, thereby causing an advance which is generally related to the increase in engine speed. The forces which restrict outward movement of the flyweights are, of course, due to the resistance offered by the tension springs 100 and 102.

It is to be noted that the cylindrical pins 96 and 98 have only vertical line contact with the usually straight sides or edges of the slots 92 and 94 and that it occurs on either side of the slot, depending upon the direction in which the weights are moving. This line contact between each cylindrical pin and the straight-edged slot is necessary because the pin is rigidly secured to the weight and the movement of the centrifugal advance mechanism is such that providing a pin with flat sides would cause binding and improper operation of the mechanism.

Assuming now that the flyweights have been positioned in accordance with engine speed, any part throttle position will cause vacuum to be communicated from orifice 18 to chamber 22 and accordingly move the diaphragm 66 to the left against the force of spring 74. The degree to which diaphragm 66 moves is basically a function of the manifold (engine) vacuum and the spring rate of spring 74.

As diaphragm 66 moves to the left, member 68 being secured thereto also moves an equivalent amount thereby causing breaker plate 46 to move in a generally clockwise direction about its pivot member 44. This movement results in the lobes of cam member 52 engaging the cam engaging portion 50 at ever increasing degrees of crankshaft rotation ahead of top dead center.

From the above it is evident that the ignition distributor provides speed responsive means for adjusting the position of cam member 52 with respect to the shaft 36 and separate pressure responsive means for rotating the breaker plate 46 and ignition contact arm assembly 48 in order to arrive at an ignition advance which is reflective of both engine load and speed.

Reference will now be made to FIGURES 4-7 which illustrate how the invention is applied to the prior art distributor of FIGURES 1-3. FIGURE 4 is, of course, a view similar to FIGURE 3, and all the identical elements are identified with the same reference numerals.

It is believed that the invention can best be descibed by initial reference to FIGURE 7 which illustrates the single-piece combination pin and slider block element 110 contemplated by the invention. The element 110 comprises a body preferably formed of some abrasion-resistant and self-lubricating material that is not as hard as the material from which the centrifugal weights 78 and or the member extending laterally from the distributor cam 52, in either of which the slots 92 and 94 may be formed, are constructed. A material found to be very suitable for the construction of the element is a relatively new plastic material known as Nylatron." The element 110 is preferably constructed so as to have three sections: a cylindrical pin section 112 at one end, a somewhat larger cylindrical section 114 having oppositely disposed parallel flat surfaces 116 at the other end, and a laterally extending flange section 118 of greater diameter than either of the two end sections.

Referring now to FIGURES 4 and 5, which illustrate one use of the member 110 shown by FIGURE 7, it is apparent that the prior art steel or other pins 96 and 98 shown in FIGURE 3 as being attached to the centrifugal weights 78 and 98, respectively, are eliminated. Rather the weights 78 and 80 are merely drilled or otherwise formed to provide bores 120 where the pins 96 and 98 would otherwise be located, and the cylindrical end 112 of the slider block and pin element 110 is inserted into each one of these bores until the flange 118 engages the upper surface of the weight. The element 90 attached to the cam 52 is then assembled over the weights 78 and 80 in a manner so that the opposite end 114 of the ele ment 110 extends into the slot 92 with the flat surfaces 116 engaging the edges of the slot. The fit, between the cylindrical end 112 of the element 110 and bore 120 in the weight is such that the element 110 can rotate freely with respect to the weight. This being so, the inward or outward movement of the weights causes a corresponding angular adjustment of the element 90, and the cam 52 to which it is attached, so as to advance or retard the spark in the same manner as explained above in connection with the prior art construction.

The combination pin and slider block element 110' is very easily and inexpensively formed from any appropriate material, and it is apparent that the elimination of the pins 96 and 98 represents a considerable saving in the cost of manufacture of this distributor spark advance mechanism. Since the element 110 is rotatable in the weights, the element has freedom of movement so as to prevent any binding inthe sliding action between the flat surfaces 116 of the element 110 and the edges of the slots 92. No hardening of any of the parts is required since the elements 110 are made of a softer material, and the element 110 has been found to require no lubrication or experience any appreciable Wear. The self-lubricating properties of the elements 110 and the provision of the flat surfaces thereon reduces the possibility of fretting corrosion, which causes mating parts subjected to high frequency and high unit load vibrations to wear due to the formation of oxides. Any roughness on the edges of the slots 92 does not materially increase the friction between these edges and the slider block portion 114 of the member .110- due to the surface contact, rather than the line contact, between these elements.

FIGURE 6 is a view similar to FIGURE 5, except that the slots 92 are formed in the weights 78 and 80, rather than in the member 90. This being so, the cylindrical portion 112 of the element 110 is fitted into bores 120 formed in the member 90' with sufficient clearance to permit rotation of the element 110 during the operation of the advance mechanism. In this particular modification, the intermediate flange 118 of the element 110, the diameter of which is greater than the width of the slots 92, prevents the element 110 from falling through the slots 92. Otherwise, the operation of FIGURE 6 is the same as that of FIGURES 4 and 5.

The overall operation of the distributors embodying the invention, as shown in FIGURES 4-7, is exactly the same as that of the prior art distributor shown in FIG- URES 1-3. It is apparent, however, that the line contact of FIGURE 3 between pins 96 and 98 and the slots 92 and 94, respectively, has been changed to a sliding surface contact in FIGURES 4 and 5. The same is true in FIGURE 6.

As already stated above, line contact between the prior art pins and slots results in very high or concentrated stresses so that normal vibrations occurring in the advance mechanism tend to and do deform the pins and the edges of the slots to the extent that the advance mechanism cannot operate properly. This malfunction due to Wear is graphically illustrated in FIGURE 8, wherein the curves A and B represent the acceptable limits of spark advance vs. engine speed, the curves C and D illustrate the performance of a new distributor and curves E and F illustrate the deviation even from the acceptable limits in a prior art distributor (FIGURES l-3) that has been subjected to the above Wear mentioned. FIGURE 8 was prepared from actual test data.

While the purpose of the invention is, of course, to maintain the operation of the distributor advance mechanism within the acceptable limits (curves A and B of FIGURE 8) throughout the distributor life, it has been found that substantially original performance (curves C and D of FIGURE 8) is achieved; in fact, the hysteresis found even in a new prior art distributor is eliminated in many instances.

From the above description, it should be apparent that a distributor embodying the invention is superior in performance as compared to prior art distributors, has longer life and is less expensive to manufacture and maintain in repair. With the use of the relatively soft combination pin and slider block elements 110, no wear occurs in the cooperating metal parts such as the weights and the cam member. If any wear or other damage occurs, it is most likely to occur in the elements which are very inexpensive and very easily replaced. This is to be contrasted with prior art distributors wherein wear requires replacement of either the weights or the cam member, since it is not practical to replace the pins alone inasmuch as they are either brazed or otherwise permanently secured to one of the elements of the spark advance mechanism.

While but two modifications of the invention have been shown and described, it is apparent that other modifications may be made. For example, it is conceivable that the element 110 may not in all cases require the oppositely disposed flat surfaces 116 in view of the fact that it is rotatable in its support, and no limitations are intended except as recited in the appended claims.

What I claim as my invention is:

1. An ignition distributor comprising a drive shaft, a pair of centrifugal weights pivoted on said shaft, a distributor cam driven by and mounted for limited rotation with respect to said shaft, said cam having a pair of arms extending therefrom in opposite directions, an angularly disposed slot form in each of said arms, and a pin rotatably mounted in each of said weights and having the free end thereof disposed in one of said slots, the end of said pin disposed in said slot having oppositely disposed parallel fiat surfaces for engagement with the edges of said slot.

2. An ignition distributor comprising a drive shaft, a pair of centrifugal weights pivoted on said shaft, a distributor cam driven by and mounted for limited rotation with respect to said shaft, said cam having a pair of arms extending therefrom in opposite directions, an angula-rly disposed slot formed in each of said weights, and a pin rotatably mounted in each of said arms and having the free end thereof disposed in one of said slots, the end of said pin disposed in said slot having oppositely disposed parallel flat surfaces for engagement with the edges of said slot.

3. An improvement in an ignition distributor of the type in which angular adjustment of the distributor cam with respect to the distributor drive shaft on which the cam is mounted is accomplished by the action between centrifugal weights pivotally mounted on said shaft and arms extending from said cam due to a pin extending from one of said elements and being in engagement with suitably disposed slots formed in the other of said elements, said improvement comprising said pins being formed and mounted on one of said elements so as to be rotatable with respect thereto, the free end of each of said pins received in one of said slots being formed with oppositely disposed flat surfaces to engage the edges of said slot.

4. An improvement in an ignition distributor of the type in which angular adjustment of the distributor cam with respect to the distributor drive shaft on which the cam is mounted is accomplished by the action between a centrifugal weight pivotally mounted on said shaft and an arm extending from said cam due to a pin extending from one of said elements and being in engagement with a suitably disposed slot formed in the other of said elements, said improvement comprising said pin being formed and mounted on one of said elements so as to be rotatable With respect thereto, the free end of said pin received in said slot being formed on opposite sides thereof so as to provide area rather than line sliding contact with the edges of said slot.

5. An ignition distributor, comprising a drive shaft, a centrifugal weight element pivoted on said shaft, a distributor cam driven by and mounted for limited rotation with respect to said shaft, said cam having an arm element extending therefrom, a suitably disposed edge formed on one of said elements, and a pin rotatably mounted on the other of said elements and having the free end thereof engaging said edge, the end of said pin engagin said edge being formed to provide area rather than line engagement with said edge.

6. An improvement in an ignition distributor of the type in which angular adjustment of the distributor cam with respect to the distributor drive shaft on which the cam is mounted is accomplished by the action between a centrifugal weight element pivotally mounted on said shaft and an arm element extending from said cam due to a pin extending from one of said elements and being in engagement with a suitably disposed edge formed on the other of said elements, said improvement comprising said pin being formed and mounted on one of said elements so as to be rotatable with respect thereto, the free contact with said edge.

5 References Cited in the file of this patent UNITED STATES PATENTS 1,029,026 Newman June 11, 1912 1,938,655 Gibson Dec. 12, 1933 2,196,360 Kamenarovic Apr. 9, 1940 10 2,977,778 Backlund et al Apr. 4, 1961 

3. AN IMPROVEMENT IN AN IGNITION DISTRIBUTOR OF THE TYPE IN WHICH ANGULAR ADJUSTMENT OF THE DISTRIBUTOR CAM WITH RESPECT TO THE DISTRIBUTOR DRIVE SHAFT ON WHICH THE CAM IS MOUNTED IS ACCOMPLISHED BY THE ACTION BETWEEN CENTRIFUGAL WEIGHTS PIVOTALLY MOUNTED ON SAID SHAFT AND ARMS EXTENDING FROM SAID CAM DUE TO A PIN EXTENDING FROM ONE OF SAID ELEMENTS AND BEING IN ENGAGEMENT WITH SUITABLY DISPOSED SLOTS FORMED IN THE OTHER OF SAID ELEMENTS, SAID IMPROVEMENT COMPRISING SAID PINS BEING FORMED AND MOUNTED ON ONE OF SAID ELEMENTS SO AS TO BE ROTATABLE WITH RESPECT THERETO, THE FREE END OF EACH OF SAID PINS RECEIVED IN ONE OF SAID SLOTS BEING FORMED WITH OPPOSITELY DISPOSED FLAT SURFACES TO ENGAGE THE EDGES OF SAID SLOT. 